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    SubjectRe: [PATCH] [request for inclusion] Realtime LSM
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    On Fri, 2005-01-14 at 03:05 +0100, utz lehmann wrote:
    > On Thu, 2005-01-13 at 16:25 -0500, Lee Revell wrote:

    > > This all seems to imply that introducing an rlimit for MAX_RT_PRIO is an
    > > excellent solution. The RT watchdog thread could run as root, and the
    > > rlimit would be used to ensure than even nonroot users in the RT group
    > > could never preempt the watchdog thread.
    >
    > Just an idea. What about throttling runaway RT tasks?
    > If the system spend more than 98% in RT tasks for 5s consider this as a
    > _fatal error_. Print an error message and throttle RT tasks by inserting
    > ticks where only SCHED_OTHER tasks allowed. For a limit of 98% this
    > means one SCHED_OTHER only tick all 50 ticks.
    >
    > The limit and timeout should be configurable and of course it can be
    > disabled.
    >

    This is just a hack. Realtime scheduling is pretty rigidly specified,
    and we satisfy that. Thus it is useful for systems that need to make
    use of it. The way SCHED_FIFO and SCHED_RR scheduling is specified is
    inherently insecure/incompatible with a multi user machine; I don't
    understand why people are getting heated with this debate. You literally
    can't run more than one realtime system on the same CPU(s) if they don't
    have a knowledge of one another.

    SCHED_FIFO and SCHED_RR are definitely privileged operations and you
    can't really change them without making them useless to legitimate
    users, I think.




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